[SECURITY-3430]

core/src/main/java/hudson/PluginManager.java

@@ -2413,6 +2413,22 @@ public String toString() {
             // only for debugging purpose
             return "classLoader " +  getClass().getName();
         }
+
+        // TODO Remove this once we require post 2024-07 remoting minimum version and deleted ClassLoaderProxy#fetchJar(URL)
+        @SuppressFBWarnings(
+                value = "DMI_COLLECTION_OF_URLS",
+                justification = "All URLs point to local files, so no DNS lookup.")
+        @Restricted(NoExternalUse.class)
+        public boolean isPluginJar(URL jarUrl) {
+            for (PluginWrapper plugin : activePlugins) {
+                if (plugin.classLoader instanceof URLClassLoader) {
+                    if (Set.of(((URLClassLoader) plugin.classLoader).getURLs()).contains(jarUrl)) {
+                        return true;
+                    }
+                }
+            }
+            return false;
+        }
     }
 
     @SuppressFBWarnings(value = "MS_SHOULD_BE_FINAL", justification = "for script console")

core/src/main/java/jenkins/security/s2m/JarURLValidatorImpl.java

@@ -0,0 +1,104 @@
+/*
+ * The MIT License
+ *
+ * Copyright (c) 2024 CloudBees, Inc.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+package jenkins.security.s2m;
+
+import edu.umd.cs.findbugs.annotations.Nullable;
+import edu.umd.cs.findbugs.annotations.SuppressFBWarnings;
+import hudson.Extension;
+import hudson.PluginManager;
+import hudson.remoting.Channel;
+import hudson.remoting.ChannelBuilder;
+import hudson.remoting.JarURLValidator;
+import java.io.IOException;
+import java.net.URL;
+import java.net.URLClassLoader;
+import java.util.Set;
+import java.util.logging.Level;
+import java.util.logging.Logger;
+import jenkins.model.Jenkins;
+import jenkins.security.ChannelConfigurator;
+import jenkins.util.SystemProperties;
+import org.kohsuke.accmod.Restricted;
+import org.kohsuke.accmod.restrictions.NoExternalUse;
+
+@Restricted(NoExternalUse.class)
+@Deprecated
+@Extension
+public class JarURLValidatorImpl extends ChannelConfigurator implements JarURLValidator {
+
+    public static final Logger LOGGER = Logger.getLogger(JarURLValidatorImpl.class.getName());
+
+    @Override
+    public void onChannelBuilding(ChannelBuilder builder, @Nullable Object context) {
+        LOGGER.log(Level.CONFIG, () -> "Setting up JarURLValidatorImpl for context: " + context);
+        builder.withProperty(JarURLValidator.class, this);
+    }
+
+    @Override
+    public void validate(URL url) throws IOException {
+        final String rejectAllProp = JarURLValidatorImpl.class.getName() + ".REJECT_ALL";
+        if (SystemProperties.getBoolean(rejectAllProp)) {
+            LOGGER.log(Level.FINE, () -> "Rejecting URL due to configuration: " + url);
+            throw new IOException("The system property '" + rejectAllProp + "' has been set, so all attempts by agents to load jars from the controller are rejected."
+                    + " Update the agent.jar of the affected agent to a version released in August 2024 or later to prevent this error."); // TODO better version spec
+        }
+        final String allowAllProp = Channel.class.getName() + ".DISABLE_JAR_URL_VALIDATOR";
+        if (SystemProperties.getBoolean(allowAllProp)) {
+            LOGGER.log(Level.FINE, () -> "Allowing URL due to configuration: " + url);
+            return;
+        }
+        if (!isAllowedJar(url)) {
+            LOGGER.log(Level.FINE, () -> "Rejecting URL: " + url);
+            throw new IOException("This URL does not point to a jar file allowed to be requested by agents: " + url + "."
+                    + " Update the agent.jar of the affected agent to a version released in August 2024 or later to prevent this error."
+            + " Alternatively, set the system property '" + allowAllProp + "' to 'true' if all the code built by Jenkins is as trusted as an administrator.");
+        } else {
+            LOGGER.log(Level.FINE, () -> "Allowing URL: " + url);
+        }
+    }
+    @SuppressFBWarnings(
+            value = "DMI_COLLECTION_OF_URLS",
+            justification = "All URLs point to local files, so no DNS lookup.")
+    private static boolean isAllowedJar(URL url) {
+        final ClassLoader classLoader = Jenkins.get().getPluginManager().uberClassLoader;
+        if (classLoader instanceof PluginManager.UberClassLoader) {
+            if (((PluginManager.UberClassLoader) classLoader).isPluginJar(url)) {
+                LOGGER.log(Level.FINER, () -> "Determined to be plugin jar: " + url);
+                return true;
+            }
+        }
+
+        final ClassLoader coreClassLoader = Jenkins.class.getClassLoader();
+        if (coreClassLoader instanceof URLClassLoader) {
+            if (Set.of(((URLClassLoader) coreClassLoader).getURLs()).contains(url)) {
+                LOGGER.log(Level.FINER, () -> "Determined to be core jar: " + url);
+                return true;
+            }
+        }
+
+        LOGGER.log(Level.FINER, () -> "Neither core nor plugin jar: " + url);
+        return false;
+    }
+}

pom.xml

@@ -87,7 +87,7 @@ THE SOFTWARE.
     <changelog.url>https://www.jenkins.io/changelog</changelog.url>
 
     <!-- Bundled Remoting version -->
-    <remoting.version>3248.v65ecb_254c298</remoting.version>
+    <remoting.version>3248.3250.v3277a_8e88c9b_</remoting.version>
     <!-- Minimum Remoting version, which is tested for API compatibility -->
     <remoting.minimum.supported.version>4.13</remoting.minimum.supported.version>
 

test/pom.xml

@@ -323,6 +323,14 @@ THE SOFTWARE.
                   <outputDirectory>${project.build.outputDirectory}/old-remoting</outputDirectory>
                   <destFileName>remoting-minimum-supported.jar</destFileName>
                 </artifactItem>
+                <artifactItem>
+                  <groupId>org.jenkins-ci.main</groupId>
+                  <artifactId>remoting</artifactId>
+                  <version>3248.v65ecb_254c298</version>
+                  <type>jar</type>
+                  <outputDirectory>${project.build.outputDirectory}/old-remoting</outputDirectory>
+                  <destFileName>remoting-before-SECURITY-3430-fix.jar</destFileName>
+                </artifactItem>
                 <artifactItem>
                   <groupId>org.jenkins-ci.main</groupId>
                   <artifactId>remoting</artifactId>